Abstract: The experimental research of the heat transfer in square annular channel with helix rib has been carried out under various thermo-hydraulic parameters in this paper. The experimental parameters are as follows, the system pressure P: 23~25 MPa; the mass flow velocity G: 600~1000 kg/（m2·s）; the heating flux q: 300~800 k W/m2; and the wrapped pitch is 160 mm.The experimental results are described in detail and the effects of pressure, mass flow and heat flux on the heat transfer are also analyzed. The comparison between the square annular channel with helix rib and bare square annular channel results indicates that the helix rib can enhance the heat transfer evidently. Based on the experimental data, a satisfactory correlation of heat transfer is given.